Personal computers ("PC's") including laptop and notebook computers and digital assistants, are becoming compact and miniaturized for convenient portability. As a result, the PC's are ;subjected to physical shock and bumps during normal use and operation. Due to the potential of corrupting data stored or else entering incorrect data, the PC's hard drive is the most vulnerable area of the computer; hence requires protection. To provide protection in the event that a physical shock is incurred, the PC's have physical shock sensors associated with the hard drives. When the sensor detects a shock, the hard drive is shut down to prevent destruction of data on the disk and damage to the read/write heads. One type of miniature reliable sensor, especially advantageous for the next generation of PC's, is a piezoelectric film sensor manufactured and sold by AMP, Inc.
One problem, however, is that the piezoelectric film sensors (being of a laminated structure) have a relatively low melting point; thus these sensors cannot withstand solder reflow temperatures normally encountered in the process of soldering these sensors to the PCB's. To overcome this problem, these peizoelectric film sensors are assembled into large plastic housings to provide thermal protection during the reflow solder process. However, the large plastic housings containing these piezoelectric film sensors cannot be used with the new smaller hard drives. Where the application dictates the use of the sensor without the large plastic housing, the film sensor is hand-soldered to the PCB after the reflow process; however, this is costly and time consuming.
Therefore, it would be highly desirable to provide a piezoelectric film sensor on the surface of a PCB, wherein the sensor is not subjected to the heat associated with reflow soldering.
Surface-mount technology for other devices or components is widely acceptable in the industry. The components are mounted and soldered directly to a surface of a PCB; and it is not necessary for the components to penetrate the PCB, thus eliminating the pre-drilled holes through the PCB. U.S. Pat. Nos. 5,145,384, 5,145,386, and 5,188,535, assigned to Molex Inc., U.S. Pat. Nos. 4,693,528, 4,955,820, 5,137,454 and 5,213,515, assigned to AMP Incorporated (the assignor of the present invention), and many others, while not in association with sensors, describe surface-mounted connectors which comprise an insulated housing having a plurality of contact receiving apertures and closely spaced contacts each mounted in respective contact-receiving apertures. The contacts engage respective contacts in the connector, and a surface-mounted soldering section is mounted on the surface of the PCB and is electrically connected to a defined conductor track or pad on the PCB. An electrical article (including another PCB, an electric component, or another connector) is inserted into the connector and is secured therein in electrical contact with the PCB.
Disadvantageously, the soldering joint is subjected to undesired exterior forces which are applied to the joint through the contact from the contacting section during insertion and removal of the electrical article. Sometimes, the force can cause the soldering section to be removed from the PCB, thus failing to provide reliable electrical contact with the PCB and repetitive product failure.
The above-described weakness of conventional surface- mounted connectors, and the risk of damage of solder joints, presents a reliability and quality assurance problem and associated warranty costs incurred by the manufacturer.
Therefore, efforts are constantly being made to design improved contact shapes to enhance the connection of electrical articles to PCBs. For instance, U.S. Pat. No. 4,455,820 describes an improved soldering portion which is capable of preventing localized concentration of forces in the soldering portion; the structure includes a large foot and a leg which, together, are shaped in the form of an inverted "T". This soldering portion minimizes the load per unit soldering area upon application of undesired external forces to the soldering joint.
In U.S. Pat. No. 5,145,384, the contacts include an inverted U-shaped portion defining a pair of depending legs; one of the legs has a foot portion for attachment to an appropriate circuit trace of the PCB. This provides some degree of yielding or flexibility in the contact, as well as between the electrical article and the PCB to relieve stresses at the soldering connections.